arXiv subjects
Publications and source records attributed to Roelof Bijker.
I present a derivation of form factors in the Algebraic Cluster Model for an arbitrary number of identical clusters. The form factors correspond to representation matrix elements which are derived in closed form for the harmonic oscillator and deformed oscillator limits. These results are relevant for applications in nuclear, molecular and hadronic physics.
In this contribution, we discuss the spin and flavor content of the proton in the framework of the unquenched quark model, and address the role of valence and sea quarks in the nucleon.
In this contribution, I discuss an algebraic treatment of alpha-cluster nuclei based on the introduction of a spectrum generating algebra for the relative motion of the alpha-clusters. Particular attention is paid to the discrete symmetry of the geometric arrangement of the alpha-particles, and the consequences for the structure of the rotational bands in the 12C and 16O nuclei.
I discuss a two-component model of nucleon form factors in which the external photon couples both to an intrinsic three-quark structure and to a meson cloud via vector-meson dominance, and present a simultaneous analysis of the electromagnetic form factors of the nucleon in the space- and time-like regions as well as their strangeness content.
We derive a general expression for the transformation brackets between the chains U(n+1) -> U(n) -> SO(n) and U(n+1) -> SO(n+1) -> SO(n).
Experimental data on electromagnetic and weak form factors of the nucleon are analyzed in a two-component model with a quark-like intrinsic structure surrounded by a meson cloud. The contribution from strange quarks is discussed and compared with recent data from the G0 Collaboration.
The concept of symmetries in physics is briefly reviewed. In the first part of these lecture notes, some of the basic mathematical tools needed for the understanding of symmetries in nature are presented, namely group theory, Lie groups and Lie algebras, and Noether's theorem. In the second part, some applications of symmetries in physics are discussed, ranging from isospin and flavor symmetry to more recent developments involving the interacting boson model and its extension to supersymmetries in nuclear physics.
In these lecture notes I discuss an algebraic model of baryons and pentaquarks, in particular a stringlike collective model is considered in which the radial excitations of baryons and pentaquarks are interpreted as rotations and vibrations of the strings. The algebraic structure of the model makes it possible to derive closed expressions for physical observables, such as masses and electromagnetic and strong couplings. The model is applied to the mass spectrum and magnetic moments of baryon resonances of the nucleon and delta families and to exotic baryons of the theta family. The ground pentaquark is predicted to have angular momentum and parity J(P)=1/2(-) and a small magnetic moment of 0.382 nuclear magnetons.
In these lecture notes I present a short review of nuclear shapes, shape coexistence and shape-phase transitions in the interacting boson model. In a study with random interactions it is shown that the appearance of regular spectral features is a far more common phenomenon than was previously thought. The origin of these features are explained by studying the relation with the underlying geometric shapes.
The phenomenom of emerging regular spectral features from random interactions is addressed in the context of the interacting boson model. A mean-field analysis links different regions of the parameter space with definite geometric shapes. The results provide a clear and transparent interpretation of the high degree of order that has been observed before in numerical studies.}